The effects of R&D and advertising on firm value: an examination of manufacturing and nonmanufacturing firms. - Yew Kee Ho; Hean Tat Keh; Jin Mei Ong (IEEE Trans. Engineering Management, 2005)

Efficiency, effectiveness and productivity of marketing in services. - Hean Tat Keh; Singfat Chu; Jiye Xu (Eur. J. Oper. Res., 2006)